Scale Removal in Domestic PVC Pipes

Vinegar.

It's not as aggressive as HCl when it hits biological systems, like human beings.

I'm unclear. what is it that is clogging the pipe? Salt you say? or is it scale? What kind of scale? Limestone? or Barium Sulfate? if it is Barium Sulfate, it is mildly radioactive and extremely resistant to chemical removal. strong HCL is required for barium sulfate or mechanical scraping, or both. if it is limestone, then a weaker HCL mix is a possibility or a strong vinegar. but vinegar might be a bit slow. Phosphoric acid may also be a possibility.

If it is salt, how in heck have you been able to drink it? I'd think drinking that much salt would be toxic.

I'd consider replacing the bends with sweeps and adding the softener.

compared to

Yes HCl reacts with salts deposits where calcium carbonate is also mixed. You have also to analyse the nature of the salts deposits then only removal is possible and selection of salt removing acid concentration is chosen. Normally in water circulating pipes calcium and magnesium carbonates get deposited and are removed by 2 to 4 N HCl. You can take salt sample and do test outside by adding said acid then go ahead accordingly.

If your pipe line is not concealed, call a plumber, cut it out at strategic opening locations manually clean it and make fresh joints. It could be a simple remedy.

Can you get Oust where you are? It is principally for de-scaling kettles. I think it's based on phosphoric acid.

A google search for "kettle de-scaler" where you are will probably get you an equivalent.

It is not so simple and it is not like kettle salt, where the salt in the water gets deposited due to boiling of the water. In above case, it is the very fine mineral salt from the bore-water gets deposited when pumped trough a compressor. The salt deposit over the months cogs the walls of the pipe and reducing the out flow to one third or less. It is very hard, like a cement block, could not be cleaned / removed by acid wash also.

Apart from the bends, the pipe length also gets affected uniformly. I made many unsuccessful attempts to remove it , but ultimately replaced the affected pipes once in 6-8 months and periodically. It is a costly affair, which includes,cost of the pipes, bends and labour

On the other hand, the Compressor was replaced by 2.0 hp Jet pump and the problem was not solved, but reduced. Now I change the PVC pipes once in 4-5 years and that too at bends only. Sridhar.

The OP said "at home".

How about replacing one more time everywhere this buildup happens with a soft flexible hose/tubing type of material. then one a month or so a simple squeezing and flexing of this tubing will break off any buildup that is starting and it can be flushed out?
Joe

SRIDHAR,

It is clear that your scaling is a harder one and needs special de scalants.

Please try the following ones on experimental basis and proceed for bulk descaling operations.

1] Get commercial toilet cleaners like HARPIC- make dilute solution of various concentrations, with temperature and soak pieces of hard scaled PVC in the solution and estimate con, time and temperature for total scale removal.

2] If PVC is not going to be chemically weakened, try combination of HCl and Sodium Hypochlorite.

3] You may also try a mixture of Phosphoric acid, formic acid with faint doses of Phenol.

Select the best and safer option based on test performance and go for bulk descaling.

Thorough after rinses with detergent and fresh water is advised to get off from traces of toxic acids

Your valuable feed back will be of immense use.

Regards.

Kevinm,

A preliminary test had been suggested. The simplest option is to be evolved based on test. Above all that, a final safe rinsing had been cautioned.

Now coming to your point on chlorine gas formation, answer which gas is being used for disinfection of drinking water supplies?

Thanks for your comments Kevinm. I draw water from a bore well of size 150 mm dia and 220 ft. deep. Since we get corporation water through taps, we do not use it for drinking & cooking, but for all other daily needs including washing machine also. The water is not salty, no sediments seen, potable. no odor and colourless too. No salt particles were seen even when filtered though a fine mesh. But in the course of time salt gets accumulated/deposited over the side walls of the PVC pipe, and I tried general treatments , de-cloggers as suggested by water experts. The foot valve is kept 15 ft from the bottom of well. When drawn through a compressor, all the dust/salt (so hard in nature, it won't even break with a normal hammering) coming along with springs is pushed up by the compressed air through the pipes. With jet, clogging does not happen, as water is drawn, and gives a longer life for the pipes. I tried special coated PVC pipes which gave more than double the life compared to ordinary ones, but settled for jet pump due to cost factor. Sridhar.

SRIDHAR, I'm a little confused, are you the OP? or are we discussing a similar but different problem? I would add one more test to your (and the OP's) testing regime. Arsenic. It is a known carcinogen, even for bathing use, and it is my understanding it is quite common in ground water, not just in south central Asia, but all over the world.

Rorschach and Sridhar:

Good suggestion Rorscharch, I do know that As is problematic in India and Bangladesh. When I sampled well water in Canada (many thousands) we included As and other metals such as Barium, Lead, and Boron. I was interested in the relationships between groundwater microbiological aspects and the metals that would be found. Believe it or not Barium, lead, and arsenic have a close relationship to bio-films and bio-fouling in groundwater (the iron and manganese bio-fouling synergy is well documented). Until we are presented good lab numbers, resolution of Sridhar's problem with scaling can be only guessed. A reasonable way to determine bio-fouling would be to sample nitrogen (NO3, NO2, NH3 all as N), Total P (bacteria do not care what form where the P comes from) and Total Organic Carbon. Elevated values point to the biofouling nature. There are more costly analysis (AOC) and for scale potential do Langlier's Index (LI). This is a calculated index based on the lab results and most labs will provide the number. Calcium Fluoride CaF2 can be problematic and produces a hard scale. Add fluoride to the testing also, it may be found in low levels but even 0.5 mg/L can be a problem.

Rorschach and Kevinm, Thanks for the details. But, Is there any practical and cost effective solution for such problems. In my view, this happens, where the ground water gets depleted continuously and not recharged due to lack of monsoon rains.

Sridhar

I don't know the geology but I suspect that you have a deeper low yielding aquifer that is isolated from the upper zone. The upper zone is likely fresh water and the deeper zone is likely very "salty". Without the monsoon recharge the upper zone is depleted by users leaving just the lower aquifer to supply water. Thus your observations of scaling during dry seasons would comply with my hypothesis. Unfortunately if there was an easy solution, practical to implement we would be irrigating our deserts long ago. If what I suspect is correct, you may want to consider building a large cistern(s) to hold rain water (when it rains) and use that water to augment your supply. You may be more atuned as to the size of the cistern needed. Salty water is most difficult to try to treat without large desalination expense. Cisterns would be very cheap in comparison. You may be able to buy trucked fresh water to fill the cistern. Sorry I can't give you the easy answers. If you don't want to spend much on analysis try to do just a simple conductivity to confirm saltiness of the water. There are very cheap portable battery conductivity units that you could use or bring the water to your provider of potable water for testing.

Thanks of your comments. In fact it is compulsory in local bodies, that we a have to save precious rain water and all the houses and public places are well equipped to collect the water from terrace / porch during monsoon rains to recharge the ground . Our ground water level was just 10 to 20 feet ten years back and it started going down over the years to 100 feet and now it will anywhere between 200 -250 ft and at places it could be even 400 feet. May be too much of water useage and poor water management, lack of storage are all could be the reasons for present problems.

You can't solve the problem until you know what the problem is. From your descriptions I'm betting on Barium Sulfate scale, and if that is what it is, Sulfuric acid is probably the only solvent that will work but there may be issues of toxicity from the byproducts, I'm not a chemist, just a poor oilfield trash mechanical knuckle dragger (mechanical designer). but until we know that, it is really hard to say what will work and what will work safely. Water and acid soluble forms of barium (Barium sulfate is not one of them) are toxic and have been used as rodenticides so we need to make sure that the end product of the reaction does not become barium sulfide which IS water soluble and is quite toxic. very strong HCL and Hydroflouric acids (separately or in combination with each other and formic acid sometimes) are often used to descale oil well sand screens that have been coated with barium scale, but oil wells don't have the issue of worrying about the toxicity of the reaction products either. You don't have that luxury.

Sounds to me that you need some kind of water treatment system targeted towards the specific chemistry of your water right at the wellhead to protect the rest of the house plumbing.

Hello Rorschach:

What is an OP? I assumed this was Sridhar's problem...Wow he really opened my eyes to some serious problems in India. At least in parts of India.

OP= Original Poster, the person that started the thread, which in this case was someone who signed in as "Guest" so we don't know who the original poster was.

Ooooooh, yes! Popular colas (brand names withheld) contain large concentrations of phosphoric acid.

so does Naval Jelly, not to be confused with KY Jelly....=b

First, I would recommend a good analysis of the water at a certified lab. You should do all major ions (Ca, Na, Total Hardness as CaCO3, Total alkalinity as CaCO3, SO4, Cl, pH, Specific Conductivity or SC at 25 degrees C, Total organic carbon, NO3, NH3, Total P, Total Fe, Fe, Ba,Total Mn, Mn, (Doing one or twenty heavy metals is easy for a lab and you may want them to report other heavy metals like Uranium ion for example if your area is in an area of granite formation). The lab results must be reliable and you should ask for a chemical balance within 5% for anions and cations compared to SC. Most labs will indicate a balance of less than this 5% arbitrary number.

Second, present these numbers to someone well versed in earth science and understands water treatment (you can try <www.mwater.ca>) for treatment design considerations. It may be possible to sequester the calcium with a polyphosphate or there may be other issues with your water supply that you are not yet aware of. For example the scale may be partial mineral salts and nuisance bacteria of iron or sulfur. Is methane an issue? Do you have current taste or odour problems?

If the water is very salty you may want to consider other options such as a shallower well with possible lots of storage to compensate for lower yields. There are many complex considerations to be explored. (Local geology,multiple aquifers in a single well, microbiology and geo-chemistry are important to understand). Conductivity profiling the well may help if you are to seek a shallower well or another well.

A dilute solution of muriatic acid or HCl (3%) would clean the calcium scale. Vinegar or citric acid would also work but would be slower than the muriatic. Sulfamic acid will also work and is frequently used to clean well screens. If the deposits are elemental sulfur you may have to physically clean the pipes with a solution of alcohol. All safety considerations should be taken. You would have to open some pipes to inspect. Once treatment has been established, replace the HWT if scaled badly as it would be cheaper than cleaning

Good Luck